Laterally diffused metal oxide semiconductor device

ABSTRACT

A semiconductor device and a related fabrication process are presented here. The device includes a support substrate, a buried oxide layer overlying the support substrate, a first semiconductor region located above the buried oxide layer and having a first conductivity type. The device also includes second, third, fourth, and fifth semiconductor regions. The second semiconductor region is located above the first semiconductor region, and it has a second conductivity type. The third semiconductor region is located above the second semiconductor region, and it has the first conductivity type. The fourth semiconductor region is located above the third semiconductor region, and it has the second conductivity type. The fifth semiconductor region extends through the fourth semiconductor region and the third semiconductor region to the second semiconductor region, and it has the second conductivity type.

TECHNICAL FIELD

Embodiments of the subject matter described herein relate generally tosemiconductor devices. More particularly, embodiments of the subjectmatter relate to a laterally diffused metal oxide semiconductor (LDMOS)device.

BACKGROUND

Semiconductor devices and semiconductor device fabrication processes arewell known. For example, metal oxide semiconductor field-effecttransistors (MOSFETs) are commonly used in a variety of differentapplications. As another example, LDMOS devices are often used inapplications, such as smart power technologies, where higher voltagerating is desired and device size is at a premium. Indeed, power LDMOSdevices are becoming increasingly popular for power applications.Furthermore, some power LDMOS devices must be designed to operate in a“high-side configuration,” which is a configuration in which all thedevice terminals are level shifted with respect to the substratepotential. A device that may be operated in a high-side configuration issaid to be “high-side capable.” High-side capable power LDMOS devicesare designed to prevent a direct punch-through path from a body regionof the power LDMOS device to an underlying, heavily doped substrate.

Existing technology attempts to satisfy high breakdown voltagerequirements by utilizing a power LDMOS device having a reduced surfacefield (RESURF) structure. A power LDMOS device having a RESURF structureincludes a first semiconductor region (which serves as a drift/RESURFregion) having one conductivity type, and a second semiconductor regionhaving a different conductivity type. The second region depletes theRESURF region from two different directions (bottom and side), allowingfor a more uniform electric field distribution and thus reducing thepeak electric field in the drift region, thereby allowing a higherbreakdown voltage for the power LDMOS device. The RESURF structure justdescribed is referred to herein as a “single RESURF” structure.

A “double RESURF” LDMOS structure, on the other hand, includes first andthird semiconductor regions having one conductivity type, and a secondsemiconductor region having a different conductivity type. In the doubleRESURF structure, first and third semiconductor regions deplete thesecond semiconductor region, thus reducing the peak electric field inthe second semiconductor region to a greater degree than is possiblewith a single RESURF structure. Transistor devices, including powerLDMOS devices and bipolar transistors, having single or double RESURFstructures, will be referred to herein as “RESURF transistors.”

Lower “on” resistance and higher breakdown voltage characteristics aredesirable in most practical LDMOS applications. An existing doubleRESURF LDMOS design utilizes a heavily doped n-type buried layer (NBL)that facilitates the double RESURF characteristics of the device.Unfortunately, the NBL limits the achievable breakdown voltage due toits depth relative to the source/body region near the surface of thedevice. Consequently, to achieve higher breakdown voltage, the thicknessof the semiconductor material (e.g., p-type epitaxial semiconductormaterial) between the NBL and the source/body region could be increased.This solution, however, may not be feasible for higher breakdown voltagerequirements, such as 80 volts and higher.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the subject matter may be derived byreferring to the detailed description and claims when considered inconjunction with the following figures, wherein like reference numbersrefer to similar elements throughout the figures.

For simplicity and clarity of illustration, the figures depict thegeneral manner of construction and certain structural elements, anddetails of well known features and characteristics may be omitted toavoid clutter and confusion. Moreover, elements in the figures are notnecessarily drawn to scale. For example, the dimensions of some of theelements in the figures may be exaggerated relative to other elements tohelp improve understanding of the described embodiments.

FIG. 1 is a cross sectional view of a portion of a semiconductor deviceaccording to an exemplary embodiment of the invention;

FIG. 2 is a cross sectional view of a portion of a semiconductor deviceaccording to another exemplary embodiment of the invention;

FIG. 3 is a cross sectional view of a portion of a semiconductor deviceaccording to yet another exemplary embodiment of the invention; and

FIG. 4 is a flow chart that illustrates a method of fabricating asemiconductor device according to an exemplary embodiment of theinvention.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the subject matter or theapplication and uses of such embodiments. As used herein, the word“exemplary” means “serving as an example, instance, or illustration.”Any implementation described herein as exemplary is not necessarily tobe construed as preferred or advantageous over other implementations.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

For the sake of brevity, conventional techniques related tosemiconductor device fabrication may not be described in detail herein.Moreover, the various tasks and process steps described herein may beincorporated into a more comprehensive procedure or process havingadditional steps or functionality not described in detail herein. Inparticular, various steps in the manufacture of semiconductor basedtransistors and other semiconductor structures are well known and so, inthe interest of brevity, many conventional steps will only be mentionedbriefly herein or will be omitted entirely without providing the wellknown process details.

FIG. 1 is a simplified cross sectional view of a portion of asemiconductor device 100 according to one exemplary embodiment.Depending upon the particular implementation, the semiconductor device100 could be a discrete component or part of an integrated circuit.Although not always required, this particular embodiment of thesemiconductor device 100 is fabricated from a semiconductor-on-insulator(SOI) substrate 102 (typically realized as a silicon-on-insulatorsubstrate), which includes a support layer 104 and/or a supportsubstrate, a buried insulator layer 106 overlying the support layer 104,and a thin layer of semiconductor material 108 overlying the buriedinsulator layer 106. The buried insulator layer 106 is typicallyrealized as a buried oxide (BOX) layer, and the layer of semiconductormaterial is usually realized as a layer of silicon material. Thehorizontal line in FIG. 1 indicates the boundary of the layer ofsemiconductor material 108. The semiconductor device 100 also includesadditional semiconductor material 110 overlying the layer ofsemiconductor material 108 and, therefore, located above the buriedinsulator layer 106. In practice, this additional semiconductor material110 may include one or more layers of the same or different types ofsemiconductor material, as explained in more detail below. In thisregard, the additional semiconductor material 110 may be formed byepitaxial growth (in one or more steps) on the layer of semiconductormaterial 108. Accordingly, the additional semiconductor material 110 maybe referred to herein as “epitaxially grown” semiconductor material.

The material used for the layer of semiconductor material 108 and theadditional semiconductor material 110 is preferably a silicon materialas typically used in the semiconductor industry, e.g., relatively puresilicon as well as silicon admixed with other elements such asgermanium, carbon, and the like. Alternatively, the semiconductormaterial can be germanium, gallium arsenide, or the like. Thesemiconductor material used for the semiconductor device 100 can bedoped to be either n-type or p-type, but is typically p-type. As usedhere, an n-type semiconductor material is a semiconductor material thathas an abundance of mobile or “carrier” electrons in the material, whilea p-type semiconductor material is a semiconductor material that has anabundance of electron acceptors or holes in the material. An n-typesilicon material can be formed by introducing an appropriate impurityspecies (e.g., phosphorus, arsenic, or antimony) into the siliconmaterial, and a p-type silicon material can be formed by introducing anappropriate impurity species (e.g., boron or aluminum) into the siliconmaterial. For this particular embodiment, the layer of semiconductormaterial 108 is a lightly doped p-type material having a dopingconcentration within the range of about 1×10¹⁵ cm⁻³ to 4×10¹⁵ cm⁻³, andthe additional semiconductor material 110 is also a lightly doped p-typematerial having the same (or a similar) doping concentration.

It should be appreciated that although the figures depict various n-typeand p-type semiconductor regions in a defined and regular arrangementand orientation, in reality these regions can be formed by implantingions of an appropriate impurity species into semiconductor material(using specified implantation energy and doses, which may vary duringthe creation of a given region). In other embodiments, these regions maybe formed by other doping methods other than implantation. Consequently,the boundary of a given n-type or p-type region need not (and typicallywill not) be as precisely defined as illustrated here. Indeed, thedoping profile within a given region may vary with its depth, width,and/or other dimensions, and the transition between adjacent regions maybe somewhat gradual, smooth, or tapered rather than immediate and abruptas depicted in the figures.

The embodiment of the semiconductor device 100 depicted in FIG. 1generally includes, without limitation: a first semiconductor region120; a second semiconductor region 122; a third semiconductor region124; a fourth semiconductor region 126; a fifth semiconductor region128; a sixth semiconductor region 130; a first semiconductor contactregion 132; a second semiconductor contact region 134; and a thirdsemiconductor contact region 136. It should be appreciated that thesixth semiconductor region 130 is realized as a ring that encircles theinterior regions of the semiconductor device 100 (e.g., the fourthsemiconductor region 126 and the fifth semiconductor region 128).Consequently, the sixth semiconductor region 130 appears as two separateregions in the cross sectional view of FIG. 1. Similarly, the firstsemiconductor contact region 132 and the second semiconductor contactregion 134 are formed as rings that encircle the interior regions of thesemiconductor device 100. Therefore, the semiconductor contact regions132, 134 are depicted in a segmented fashion in the cross sectional viewof FIG. 1.

The illustrated embodiment of the semiconductor device 100 also includesa gate electrode structure 138. Although the gate electrode structure138 is realized as a ring-shaped element, it appears segmented in thecross sectional view of FIG. 1 (as explained above for the sixthsemiconductor region 130). In practice, the gate electrode structure 138can be formed using a polycrystalline silicon material, which isseparated from the underlying semiconductor material by a thindielectric layer, e.g., a gate oxide layer. This gate oxide can bethermally grown or deposited, in accordance with conventionaltechniques.

The semiconductor device 100 includes an isolation region 140 thatfunctions to electrically isolate the semiconductor device from otherdevices and/or components (not shown) that might be formed elsewhere onthe same wafer. The semiconductor device 100 also includes an isolationregion 142 that functions as the field drift region used to reducesurface electric field. In typical deployments, the isolation regions140, 142 are realized using field oxide or shallow trench isolation(STI) oxide, as is well understood. As shown in FIG. 1, thepolycrystalline silicon material of the gate electrode structure extendsfrom the first semiconductor contact region 132 (the source region) toroughly the center of the isolation region 142.

It should be appreciated that the semiconductor device 100 represents anembodiment of RESURF transistor structure. More specifically, thesemiconductor device 100 represents an embodiment of a double-doubleRESURF LDMOS transistor structure. In this regard, the thirdsemiconductor contact region 136 may serve as a drain contact forcoupling to a suitable drain voltage terminal 150, and the first andsecond semiconductor contact regions 132, 134 may be tied together toserve as a body/source contact for coupling to a suitable body/sourcevoltage terminal 152. Moreover, the gate electrode structure 138 may becoupled to a suitable gate voltage terminal 154. The voltages applied tothe drain voltage terminal 150, the body/source voltage terminal 152,and the gate voltage terminal 154 will influence the operatingcharacteristics of the semiconductor device.

Referring again to the illustrated configuration of the semiconductordevice 100, the additional semiconductor material 110 has a firstconductivity type (which is p-type for this particular example). Thefirst semiconductor region 120 is realized as a section or a portion ofthe additional semiconductor material 110. In other words, at least someof the additional semiconductor material 110 forms the firstsemiconductor region 120, which need not be precisely defined as aspecific volume within the additional semiconductor material 110.Accordingly, the first semiconductor region 120 has a first conductivitytype (which is p-type for this particular example). As shown in FIG. 1,the first semiconductor region 120 is located above the buried insulatorlayer 106 and above the layer of semiconductor material 108. Moreover,at least a portion of the first semiconductor region 120 is locatedbelow the second semiconductor region 122.

The second semiconductor region 122 is also located in the additionalsemiconductor material 110, however, it has a second conductivity type(which is n-type for this particular example). In practice, the secondsemiconductor region 122 may be formed as an implant region byimplanting a portion of the additional semiconductor material 110 withan appropriate impurity species such that the second semiconductorregion 122 has a doping concentration within the range of about 1×10¹⁶cm⁻³ to 1×10¹⁷ cm⁻³. The second semiconductor region 122 is generallylocated above the first semiconductor region 120, below the thirdsemiconductor region 124, and below the fifth semiconductor region 128.Although not always necessary, the second semiconductor region 122 is atleast partially contiguous with the first semiconductor region 120.Moreover, in certain embodiments (such as the illustrated embodiment),the second semiconductor region 122 is formed such that little to noportion of it is located under the sixth semiconductor region 130. Inother words, the inner boundary or edge of the ring-shaped sixthsemiconductor region 130 does not overlap any section of the outerboundary or edge of the second semiconductor region 122. In otherexemplary embodiments, however, the second semiconductor region 122could extend laterally (e.g., horizontally in FIG. 1) below, andpossibly beyond, the sixth semiconductor region 130. The height of thesecond semiconductor region 122 (e.g., the vertical dimension in FIG. 1)may be within the range of about 1.0 μm to about 2.0 μm, withoutlimitation.

The third semiconductor region 124 is located in the additionalsemiconductor material 110, and it has the first conductivity type(p-type for this example). In practice, the third semiconductor region124 may be formed as an implant region by implanting a portion of theadditional semiconductor material 110 with an appropriate impurityspecies such that the third semiconductor region 124 has a dopingconcentration within the range of about 1×10¹⁶ cm⁻³ to 1×10¹⁷ cm⁻³. Thethird semiconductor region 124 is generally located above the secondsemiconductor region 122 and below the fourth semiconductor region 126.Although not always necessary, the third semiconductor region 124 is atleast partially contiguous with the second semiconductor region 122. Incertain embodiments (such as the illustrated embodiment), the thirdsemiconductor region 124 is formed such that little to no portion of itis located under the sixth semiconductor region 130, as described abovefor the second semiconductor region 122. Although not always required,the lateral boundary of the third semiconductor region 124 is alignedwith the lateral boundary of the second semiconductor region 122 (asdepicted in FIG. 1). In other exemplary embodiments, however, the secondand third semiconductor regions 122, 124 need not share a common lateralboundary and/or the third semiconductor region 124 could extendlaterally below, and possibly beyond, the sixth semiconductor region130. The height of the third semiconductor region 124 (e.g., thevertical dimension in FIG. 1) may be within the range of about 1.0 μm toabout 2.0 μm, without limitation. Moreover, in certain embodiments thesecond and third semiconductor regions 122, 124 have the same nominalheight.

The fourth semiconductor region 126 is also located in the additionalsemiconductor material 110, but it has the second conductivity type(n-type for this example). In practice, the fourth semiconductor region126 may be formed as an implant region by implanting a portion of theadditional semiconductor material 110 with an appropriate impurityspecies such that the fourth semiconductor region 126 has a dopingconcentration within the range of about 1×10¹⁶ cm⁻³ to 1×10¹⁷ cm⁻³. Thefourth semiconductor region 126 is generally located above the thirdsemiconductor region 124, near or at the upper surface of thesemiconductor device 100. Although not always necessary, the fourthsemiconductor region 126 is at least partially contiguous with the thirdsemiconductor region 124. In certain embodiments (such as theillustrated embodiment), the fourth semiconductor region 126 is adjacentto and separated from the sixth semiconductor region 130. In otherembodiments, the fourth semiconductor region 126 may be immediatelyadjacent to (i.e., contiguous with) the sixth semiconductor region 130.Although not always required, the lateral boundary of the fourthsemiconductor region 126 is aligned with the lateral boundaries of thesecond and third semiconductor regions 122, 124 (as depicted in FIG. 1).In other exemplary embodiments, however, the second, third, and fourthsemiconductor regions 122, 124, 126 need not share a common lateralboundary. The height of the fourth semiconductor region 126 (e.g., thevertical dimension in FIG. 1) may be within the range of about 1.0 μm toabout 2.0 μm, without limitation. Moreover, in certain embodiments thesecond, third, and fourth semiconductor regions 122, 124, 126 have thesame nominal height.

The fifth semiconductor region 128 is located in the additionalsemiconductor material 110, and it has the second conductivity type(n-type for this example). In practice, the fifth semiconductor region128 may be formed as an implant region by implanting a portion of theadditional semiconductor material 110 with an appropriate impurityspecies such that the fifth semiconductor region 128 has a dopingconcentration within the range of about 5×10¹⁶ cm⁻³ to 8×10¹⁷ cm⁻³. Thefifth semiconductor region 128 is generally located above the secondsemiconductor region 122, and it extends from a point at or near theupper surface of the semiconductor device 100 to the secondsemiconductor region 122. In this regard, the fifth semiconductor region128 can be formed such that it extends through the third and fourthsemiconductor regions 124, 126, and such that portions of the third andfourth semiconductor regions 124, 126 encircle the fifth semiconductorregion 128. Thus, in the illustrated embodiment, the fifth semiconductorregion 128 is adjacent to and at least partially contiguous with boththe third and fourth semiconductor regions 124, 126.

For this exemplary embodiment, the third semiconductor contact region136 is associated with the drain region of the semiconductor device 100.The third semiconductor contact region 136 is located in the fifthsemiconductor region 128, at or near the upper surface of thesemiconductor device 100, and it has the second conductivity type(n-type for this example). In practice, the third semiconductor contactregion 136 may be formed as an implant region by implanting a portion ofthe additional semiconductor material 110 with an appropriate impurityspecies such that the third semiconductor contact region 136 has arelatively heavy doping concentration within the range of about 1×10²⁰cm⁻³ to 1×10²¹ cm⁻³. As mentioned above, the third semiconductor contactregion 136 may be coupled to the drain voltage terminal 150. Moreover,the third semiconductor contact region 136 is electrically coupled tothe fifth semiconductor region 128, which in turn is electricallycoupled to the second semiconductor region 122 and the fourthsemiconductor region 126.

The sixth semiconductor region 130 is located in the additionalsemiconductor material 110, and it has the first conductivity type(p-type for this example). In practice, the sixth semiconductor region130 may be formed as an implant region by implanting a portion of theadditional semiconductor material 110 with an appropriate impurityspecies such that the sixth semiconductor region 130 has a dopingconcentration within the range of about 5×10¹⁶ cm⁻³ to 8×10¹⁷ cm⁻³. Thesixth semiconductor region 130 is located at or near the upper surfaceof the semiconductor device 100, and adjacent to the fourthsemiconductor region 126. For this particular embodiment, the sixthsemiconductor region 130 resembles a ring that encircles the fourthsemiconductor region 126. Moreover, the fourth semiconductor region 126separates the fifth semiconductor region 128 from the sixthsemiconductor region 130, as depicted in FIG. 1. In other words, thesixth semiconductor region 130 is spaced away from the fifthsemiconductor region 128, and the fourth semiconductor region 126resides between the fifth and sixth semiconductor regions 128, 130. Inpractice, the sixth semiconductor region 130 can be formed to a depth ofabout 1.0 μm to about 2.0 μm, without limitation. Therefore, dependingupon the particular embodiment, the lowermost boundary of the sixthsemiconductor region 130 may be higher than the lowermost boundary ofthe fourth semiconductor region 126, or it may extend downward to anydesired depth.

For this example, the first semiconductor contact region 132 isassociated with the source region of the semiconductor device 100. Thefirst semiconductor contact region 132 is located in the sixthsemiconductor region 130, at or near the upper surface of thesemiconductor device 100, and it has the second conductivity type(n-type for this example). In practice, the first semiconductor contactregion 132 may be formed as an implant region by implanting a portion ofthe additional semiconductor material 110 with an appropriate impurityspecies such that the first semiconductor contact region 132 has arelatively heavy doping concentration within the range of about 1×10²⁰cm⁻³ to 1×10²¹ cm⁻³. As mentioned above, the first semiconductor contactregion 132 may be coupled to the body/source voltage terminal 152.

For this example, the second semiconductor contact region 134 isassociated with the body region of the semiconductor device 100. Thesecond semiconductor contact region 134 is located in the sixthsemiconductor region 130, at or near the upper surface of thesemiconductor device 100, and adjacent to the first semiconductorcontact region 132. The second semiconductor contact region 134 has thefirst conductivity type (p-type for this example). In practice, thesecond semiconductor contact region 134 may be formed as an implantregion by implanting a portion of the additional semiconductor material110 with an appropriate impurity species such that the secondsemiconductor contact region 134 has a relatively heavy dopingconcentration within the range of about 1×10²⁰ cm⁻³ to 1×10²¹ cm⁻³. Asmentioned above, the second semiconductor contact region 134 may becoupled to the body/source voltage terminal 152. Moreover, the secondsemiconductor contact region 134 is electrically coupled to the sixthsemiconductor region 130.

The different doping concentrations of the various semiconductor regionsof the semiconductor device 100 cooperate to provide the double-doubleRESURF LDMOS operating characteristics. In this regard, the fifthsemiconductor region 128 is more heavily doped than any of the first,second, third, or fourth semiconductor regions 120, 122, 124, 126.Likewise, the sixth semiconductor region 130 is more heavily doped thanany of the first, second, third, or fourth semiconductor regions 120,122, 124, 126. Moreover, the additional semiconductor material 110 (and,therefore, the first semiconductor region 120) is more lightly dopedthan any of the second, third, fourth, fifth, or sixth semiconductorregions 122, 124, 126, 128, 130.

As power technologies develop, power applications require smaller andsmaller power LDMOS devices with improved voltage capability. Highvoltage power LDMOS devices in deep sub-micrometer (sub-micron)technologies are difficult to design, however, in part due to limitedepitaxial layer thickness and limited thermal budget. Accordingly, thereis a need for a double RESURF LDMOS device having improved on-stateperformance (low on-state resistance) characteristics and having astructure that can tolerate relatively high breakdown voltagerequirements.

The semiconductor device 100 exhibits improved safe operating area (SOA)and electrostatic discharge (ESD) capabilities by utilizing a deep drainstructure for LDMOS design. The semiconductor device 100 employs adouble-double RESURF LDMOS arrangement to further improve the off-statecapability enabled by a uniform potential distribution with optimizedon-state performance. The presence of the p-type semiconductor materialunder the n-type second semiconductor region 122, along with the buriedinsulator layer 106, retains the double-double RESURF action and, inturn, a more uniform electric field. More specifically, the thirdsemiconductor region 124 is depleted from both the overlying fourthsemiconductor region 126 and the underlying second semiconductor region122, while the second semiconductor region 122 is depleted from both theoverlying third semiconductor region 124 and the underlying firstsemiconductor region 120.

Notably, the semiconductor device 100 employs the following verticalarrangement (from top to bottom): second conductivity type region; firstconductivity type region; second conductivity type region; firstconductivity type region; buried insulator layer. The semiconductordevice 100 utilizes thick SOI technology that allows for full high-sidecapability without requiring the use of a heavily doped n-type buriedlayer (NBL). In other words, the buried insulator layer obviates theneed for an NBL. Accordingly, because an NBL is not required for highside capability, there is no maximum voltage restriction due to spacingbetween the NBL and body well and, therefore, no thicker epitaxialmaterial requirement for higher breakdown voltage.

FIG. 2 is a cross sectional view of a portion of a semiconductor device200 according to another exemplary embodiment of the invention. Many ofthe features, elements, and structures of the semiconductor device 200are similar or identical to those described above for the semiconductordevice 100, and such common items will not be redundantly described indetail here. The semiconductor device 200 differs from the semiconductordevice 100 in that it includes an eighth semiconductor region 202located in the additional semiconductor material 110, and having thefirst conductivity type (p-type for this example). Notably, the eighthsemiconductor region 202 may be used in lieu of or in addition to thefirst semiconductor region 120 (not shown in FIG. 2). In practice, theeighth semiconductor region 202 may be formed as an implant region byimplanting a portion of the additional semiconductor material 110 withan appropriate impurity species such that the eighth semiconductorregion 202 has a doping concentration within the range of about 1×10¹⁶cm⁻³ to 1×10¹⁷ cm⁻³. The higher doping concentration in the eighthsemiconductor region 202 (relative to the doping concentration in thesurrounding additional semiconductor material 110) results in a strongerdepletion into the second semiconductor region 122.

For the embodiment shown in FIG. 2, the eighth semiconductor region 202is located above the buried insulator layer 106, but below the secondsemiconductor region 122. Although not always necessary, the eighthsemiconductor region 202 is at least partially contiguous with thesecond semiconductor region 122. Moreover, although not always required,the lateral boundary of the eighth semiconductor region 202 is alignedwith the lateral boundaries of the second, third, and fourthsemiconductor regions 122, 124, 126 (as depicted in FIG. 1). In otherexemplary embodiments, however, the second, third, fourth, and eighthsemiconductor regions 122, 124, 126, 202 need not share a common lateralboundary. The height of the eighth semiconductor region 202 (e.g., thevertical dimension in FIG. 2) may be within the range of about 1.0 μm toabout 2.0 μm, without limitation. In certain embodiments, the second,third, fourth, and eighth semiconductor regions 122, 124, 126, 202 havethe same nominal height.

FIG. 3 is a cross sectional view of a portion of a semiconductor device300 according to another exemplary embodiment of the invention. Many ofthe features, elements, and structures of the semiconductor device 300are similar or identical to those described above for the semiconductordevice 100, and such common items will not be redundantly described indetail here. The semiconductor device 300 differs from the semiconductordevice 100 in that it includes an eighth semiconductor region 302located in the additional semiconductor material 110, and having thefirst conductivity type (p-type for this example). For this embodiment,the eighth semiconductor region 302 is used with the first semiconductorregion 120, which resides between the second and eighth semiconductorregions 122, 302. In practice, the eighth semiconductor region 302 maybe formed as a implant region by blanket implanting the additionalsemiconductor material 110 with an appropriate impurity species suchthat the eighth semiconductor region 302 has a doping concentrationwithin the range of 1×10¹⁶ cm⁻³ to 1×10¹⁷ cm⁻³. The higher dopingconcentration in the eighth semiconductor region 302 (relative to thedoping concentration in the surrounding additional semiconductormaterial 110) results in a stronger depletion into the secondsemiconductor region 122.

For the embodiment shown in FIG. 3, the eighth semiconductor region 302is located above the buried insulator layer 106, but below the firstsemiconductor region 120. In alternate embodiments, the eighthsemiconductor region 302 is at least partially contiguous with thesecond semiconductor region 122, i.e., there is little to no “gap”between the second and eighth semiconductor regions 122, 302. Notably,the eighth semiconductor region 302 laterally extends beyond the lateralboundaries of the second, third, and fourth semiconductor regions 122,124, 126. Indeed, due to the blanket nature of the implant used tocreate the eighth semiconductor region 302, it extends below (andpossibly beyond) the sixth semiconductor region 130. The height of theeighth semiconductor region 302 (e.g., the vertical dimension in FIG. 3)may be within the range of about 1.0 μm to about 2.0 μm, withoutlimitation. In certain embodiments, the second, third, fourth, andeighth semiconductor regions 122, 124, 126, 302 have the same nominalheight.

Refer now to FIG. 4, which is a flow chart that illustrates a process400 of fabricating a semiconductor device according to an exemplaryembodiment of the invention. The process 400 may begin by providing anappropriate SOI substrate having a support layer, a buried insulatorlayer (e.g., a BOX layer) overlying the support layer, and a layer ofsemiconductor material overlying the buried insulator layer (task 402).In practice, the SOI substrate could be obtained from a wafer vendor orsupplier. In a typical embodiment, the thickness of the original layerof semiconductor material is about 1.5 μm. The process 400 may continueby forming a first layer of additional semiconductor material overlyingthe semiconductor material on the SOI substrate (task 404), where theadditional semiconductor material has a first conductivity type (whichis p-type for this example). Task 404 may be performed by epitaxiallygrowing an initial layer of additional semiconductor material on theexisting semiconductor material of the SOI substrate, using well knownepitaxial growth technology and processing. Moreover, the additionalsemiconductor material may be in-situ doped or it may be doped by ionimplantation after it has been grown. In a typical embodiment, thethickness of the initial layer of additional semiconductor material isabout 2.0 μm. Notably, at least a portion of the epitaxially grownsemiconductor material may serve as a first semiconductor region of theresulting semiconductor device (e.g., the first semiconductor region 120shown in FIG. 1 and FIG. 3).

As explained above with reference to FIG. 2 and FIG. 3, the resultingsemiconductor device may include an optional lower semiconductor regionhaving the first conductivity type (e.g., the eighth semiconductorregion 202, 302). If this lower region will not be fabricated (querytask 406), then the process 400 continues by forming a secondsemiconductor region (e.g., the second semiconductor region 122) in theinitial layer of additional semiconductor material (task 408). Incertain embodiments, this second semiconductor region can be formed bycreating an appropriate ion implantation mask that defines the desiredimplantation boundary, and then implanting ions of an impurity speciesinto the initial layer of additional semiconductor material such thatthe second semiconductor region has the second conductivity type (n-typefor this example). After formation of the second semiconductor region,the process 400 performs a task 414 (described below).

If, however, a lower semiconductor region will be fabricated (query task406), then the process continues by forming an eighth semiconductorregion (e.g., the eighth semiconductor region 202, 302) in the initiallayer of additional semiconductor material (task 410). In someembodiments, this eighth semiconductor region is formed by creating anappropriate ion implantation mask that defines the desired implantationboundary, and then implanting ions of an impurity species into theinitial layer of additional semiconductor material such that the eighthsemiconductor region has the first conductivity type (p-type for thisexample). In other embodiments, the eighth semiconductor region isformed by a blanket ion implantation procedure without using any ionimplantation mask, such that a blanket layer having the firstconductivity type is created in the initial layer of additionalsemiconductor material.

After formation of the eighth semiconductor region, the process 400 maycontinue by forming a second semiconductor region (e.g., the secondsemiconductor region 122) in the initial layer of additionalsemiconductor material and above the eighth semiconductor region (task412). In certain embodiments, this second semiconductor region can beformed by creating an appropriate ion implantation mask that defines thedesired implantation boundary, and then implanting ions of an impurityspecies into the initial layer of additional semiconductor material suchthat the second semiconductor region has the second conductivity type(n-type for this example).

After formation of the second semiconductor region (by way of task 408or task 412), the process 400 forms a second layer of additionalsemiconductor material (having the first conductivity type, e.g.,p-type) overlying the initial layer of additional semiconductor material(task 414). In practice, the second layer of additional semiconductormaterial and the initial layer of additional semiconductor material areformed from the same type of material. Task 414 may be performed byepitaxially growing the second layer of additional semiconductormaterial on the exposed semiconductor material, using well knownepitaxial growth technology and processing. Moreover, the additionalsemiconductor material may be in-situ doped or it may be doped by ionimplantation after it has been grown. In a typical embodiment, thethickness of the second layer of additional semiconductor material isabout 2.5 μm. The use of two (or more) distinct epitaxial growth stepsis desirable to accommodate ion implantation for semiconductor regionsthat might otherwise be too deep for some ion implantation tools.

The process 400 may continue by forming a third semiconductor region(e.g., the third semiconductor region 124) in the second layer ofadditional semiconductor material (task 416) and by forming a fourthsemiconductor region (e.g., the fourth semiconductor region 126) in thesecond layer of additional semiconductor material (task 418). The thirdsemiconductor region has the first conductivity type (p-type in thisexample), and it is located above the second semiconductor region. Thefourth semiconductor region has the second conductivity type (n-type inthis example), and it is located above the third semiconductor region.In certain embodiments, the third and fourth semiconductor regions canbe formed by creating an appropriate ion implantation mask that definesthe desired implantation boundary, and then performing a chain implantprocedure to create the p-type implant for the third semiconductorregion and the n-type implant for the fourth semiconductor region. Forthe illustrated example, the ion implantation mask used to implant thethird and fourth semiconductor regions 124, 126 defines a ring shapedopening such that a portion of underlying material within the centralportion of the ring remains protected.

The process 400 also forms a fifth semiconductor region (e.g., the fifthsemiconductor region 128) in the second layer of additionalsemiconductor material (task 420) and a sixth semiconductor region(e.g., the sixth semiconductor region 130) in the second layer ofadditional semiconductor material (task 422). As described above, thefifth semiconductor region extends through the third and fourthsemiconductor regions to the second semiconductor region, and the fifthsemiconductor is formed such that it has the second conductivity type(n-type for this example). The sixth semiconductor region is formedaround and adjacent to the fourth semiconductor region, and the sixthsemiconductor region is formed such that it has the first conductivitytype (p-type for this example). The fifth and sixth semiconductorregions can be created by forming ion implantation masks and byimplanting ions of the appropriate impurity species into the secondlayer of additional semiconductor material.

Next, the process 400 forms the gate structure for the device (e.g., thegate electrode structure 138), in accordance with an appropriate gatefabrication procedure or module (task 423). For example, task 423 mayinvolve various material deposition, photolithography, and etching stepsthat result in the creation of a ring-shaped gate insulator, aring-shaped polycrystalline silicon gate electrode, and sidewall spacersadjacent the sidewalls of the gate electrode (see FIG. 1). As shown inFIG. 1, the resulting gate electrode structure 138 “straddles” or“bridges” the fourth and sixth semiconductor regions 126, 130.

The process 400 can then perform a task 424 to create semiconductorcontact regions in the fifth semiconductor region (e.g., the contactregion 136) and in the sixth semiconductor region (e.g., the contactregions 132, 134). These semiconductor contact regions can be created byforming ion implantation masks and by implanting ions of the appropriateimpurity species into the fifth and sixth semiconductor regions. Forthis particular example, these implanting steps create the source,drain, and body implants for the device.

In summary, systems, devices, and methods configured in accordance withexemplary embodiments relate to:

A semiconductor device having: a semiconductor-on-insulator substratecomprising a support layer, a buried insulator layer overlying thesupport layer, and a layer of semiconductor material overlying theburied insulator layer; additional semiconductor material overlying thelayer of semiconductor material, the additional semiconductor materialcomprising a first semiconductor region having a first conductivitytype; a second semiconductor region located in the additionalsemiconductor material and having a second conductivity type; a thirdsemiconductor region located in the additional semiconductor materialabove the second semiconductor region and having the first conductivitytype; a fourth semiconductor region located in the additionalsemiconductor material above the third semiconductor region and havingthe second conductivity type; and a fifth semiconductor region locatedin the additional semiconductor material above the second semiconductorregion and having the second conductivity type, the fifth semiconductorregion being adjacent to both the third semiconductor region and thefourth semiconductor region.

The semiconductor device may further include a semiconductor contactregion located in the fifth semiconductor region, and having the secondconductivity type. In such a device, the fifth semiconductor regioncould electrically couple the second semiconductor region and the fourthsemiconductor region to the semiconductor contact region.

The semiconductor device may further include a sixth semiconductorregion located in the additional semiconductor material adjacent to thefourth semiconductor region and having the first conductivity type. Sucha device may further include a seventh semiconductor region located inthe sixth semiconductor region and having the second conductivity type.In such a device, the fourth semiconductor region could separate thefifth semiconductor region from the sixth semiconductor region. Anembodiment of such a device could be fabricated such that no portion ofthe second semiconductor region is located under the sixth semiconductorregion. An embodiment of such a device could be fabricated such that noportion of the third semiconductor region is located under the sixthsemiconductor region. Such a device may further include a gate structurethat overlies a portion of the fourth semiconductor region and overliesa portion of the sixth semiconductor region. In such a device, the fifthsemiconductor region could serve as a drain region of a transistor, thesixth semiconductor region could serve as a source region of thetransistor, and the gate structure could serve as the gate of thetransistor.

The semiconductor device may further include an eighth semiconductorregion located in the additional semiconductor material above the buriedinsulator layer and below the second semiconductor region, and havingthe first conductivity type. In such a device, the eighth semiconductorregion could laterally extend beyond lateral boundaries of the secondsemiconductor region, the third semiconductor region, and the fourthsemiconductor region.

In certain embodiments, the fifth semiconductor region is more heavilydoped than any of the second semiconductor region, the thirdsemiconductor region, and the fourth semiconductor region, and theadditional semiconductor material is more lightly doped than any of thesecond semiconductor region, the third semiconductor region, and thefourth semiconductor region.

A semiconductor device formed on a support substrate. The semiconductordevice includes: a buried oxide layer overlying the support substrate; afirst semiconductor region located above the buried oxide layer andhaving a first conductivity type; a second semiconductor region locatedabove the first semiconductor region and having a second conductivitytype; a third semiconductor region located above the secondsemiconductor region and having the first conductivity type; a fourthsemiconductor region located above the third semiconductor region andhaving the second conductivity type; and a fifth semiconductor regionextending through the fourth semiconductor region and the thirdsemiconductor region to the second semiconductor region, and having thesecond conductivity type.

The semiconductor device may further include epitaxially grownsemiconductor material located above the buried oxide layer, wherein:the first semiconductor region comprises a portion of the epitaxiallygrown semiconductor material; and the second semiconductor region, thethird semiconductor region, the fourth semiconductor region, and thefifth semiconductor region are all located in the epitaxially grownsemiconductor material.

The semiconductor device may further include a semiconductor contactregion located in the fifth semiconductor region and having the secondconductivity type, wherein the fifth semiconductor region electricallycouples the second semiconductor region to the semiconductor contactregion.

The semiconductor device may further include: a layer of semiconductormaterial overlying the buried oxide layer; and epitaxially grownsemiconductor material overlying the layer of semiconductor material;wherein: the first semiconductor region comprises a portion of theepitaxially grown semiconductor material; and the second semiconductorregion, the third semiconductor region, the fourth semiconductor region,and the fifth semiconductor region are all located in the epitaxiallygrown semiconductor material.

A method of fabricating a semiconductor device on asemiconductor-on-insulator substrate comprising a support layer, aburied insulator layer overlying the support layer, and a layer ofsemiconductor material overlying the buried insulator layer. The methodinvolves: forming epitaxially grown semiconductor material overlying thelayer of semiconductor material, the epitaxially grown semiconductormaterial having a first conductivity type, and at least a portion of theepitaxially grown semiconductor material serving as a firstsemiconductor region of the semiconductor device; forming a secondsemiconductor region in the epitaxially grown semiconductor material,the second semiconductor region located above the first semiconductorregion and having a second conductivity type; forming a thirdsemiconductor region in the epitaxially grown semiconductor material,the third semiconductor region located above the second semiconductorregion and having the first conductivity type; forming a fourthsemiconductor region in the epitaxially grown semiconductor material,the fourth semiconductor region located above the third semiconductorregion and having the second conductivity type; and forming a fifthsemiconductor region in the epitaxially grown semiconductor material,the fifth semiconductor region extending through the fourthsemiconductor region and the third semiconductor region to the secondsemiconductor region, and having the second conductivity type.

The step of forming the epitaxially grown semiconductor material mayinvolve: forming a first layer of epitaxially grown semiconductormaterial overlying the layer of semiconductor material; and forming asecond layer of epitaxially grown semiconductor material overlying thefirst layer of epitaxially grown semiconductor material; wherein thesecond semiconductor region is formed in the first layer of epitaxiallygrown semiconductor material before forming the second layer ofepitaxially grown semiconductor material; and the third semiconductorregion, the fourth semiconductor region, and the fifth semiconductorregion are formed in the second layer of epitaxially grown semiconductormaterial.

The method may further involve forming a semiconductor contact region inthe fifth semiconductor region, the semiconductor contact region havingthe second conductivity type, wherein the fifth semiconductor regionelectrically couples the second semiconductor region to thesemiconductor contact region.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. For example, although the example presentedabove is for an n-LDMOS device (where the “first conductivity type” isp-type and the “second conductivity type” is n-type), the techniques andtechnology described above also apply to a p-LDMOS device (where the“first conductivity type” is n-type and the “second conductivity type”is p-type). It should also be appreciated that the exemplary embodimentor embodiments described herein are not intended to limit the scope,applicability, or configuration of the claimed subject matter in anyway. Rather, the foregoing detailed description will provide thoseskilled in the art with a convenient road map for implementing thedescribed embodiment or embodiments. It should be understood thatvarious changes can be made in the function and arrangement of elementswithout departing from the scope defined by the claims, which includesknown equivalents and foreseeable equivalents at the time of filing thispatent application.

1. A semiconductor device comprising: a semiconductor-on-insulatorsubstrate comprising a support layer, a buried insulator layer overlyingthe support layer, and a layer of semiconductor material overlying theburied insulator layer; additional semiconductor material overlying thelayer of semiconductor material, the additional semiconductor materialcomprising a first semiconductor region having a first conductivitytype; a second semiconductor region located in the additionalsemiconductor material and having a second conductivity type; a thirdsemiconductor region located in the additional semiconductor materialabove the second semiconductor region and having the first conductivitytype; a fourth semiconductor region located in the additionalsemiconductor material above the third semiconductor region and havingthe second conductivity type; a fifth semiconductor region located inthe additional semiconductor material above the second semiconductorregion and having the second conductivity type, the fifth semiconductorregion being adjacent to both the third semiconductor region and thefourth semiconductor region; and a sixth semiconductor region located inthe additional semiconductor material adjacent to the fourthsemiconductor region and having the first conductivity type, wherein noportion of the second semiconductor region is located under the sixthsemiconductor region.
 2. The semiconductor device of claim 1, furthercomprising a semiconductor contact region located in the fifthsemiconductor region, and having the second conductivity type.
 3. Thesemiconductor device of claim 2, wherein the fifth semiconductor regionelectrically couples the second semiconductor region and the fourthsemiconductor region to the semiconductor contact region.
 4. Thesemiconductor device of claim 1, further comprising a semiconductorcontact region located in the sixth semiconductor region and having thesecond conductivity type.
 5. The semiconductor device of claim 1,wherein the fourth semiconductor region separates the fifthsemiconductor region from the sixth semiconductor region.
 6. Thesemiconductor device of claim 1, wherein no portion of the thirdsemiconductor region is located under the sixth semiconductor region. 7.The semiconductor device of claim 1, further comprising a gate structurethat overlies a portion of the fourth semiconductor region and overliesa portion of the sixth semiconductor region.
 8. The semiconductor deviceof claim 7, wherein: the fifth semiconductor region serves as a drainregion of a transistor; the sixth semiconductor region serves as asource region of the transistor; and the gate structure serves as thegate of the transistor.
 9. The semiconductor device of claim 1, furthercomprising an eighth semiconductor region located in the additionalsemiconductor material above the buried insulator layer and below thesecond semiconductor region, and having the first conductivity type. 10.The semiconductor device of claim 1, wherein: the fifth semiconductorregion is more heavily doped than any of the second semiconductorregion, the third semiconductor region, and the fourth semiconductorregion; and the additional semiconductor material is more lightly dopedthan any of the second semiconductor region, the third semiconductorregion, and the fourth semiconductor region.
 11. A semiconductor deviceformed on a support substrate, the semiconductor device comprising: aburied oxide layer overlying the support substrate; a firstsemiconductor region located above the buried oxide layer and having afirst conductivity type; a second semiconductor region located above thefirst semiconductor region and having a second conductivity type; athird semiconductor region located above the second semiconductor regionand having the first conductivity type; a fourth semiconductor regionlocated above the third semiconductor region and having the secondconductivity type; a fifth semiconductor region extending through thefourth semiconductor region and the third semiconductor region to thesecond semiconductor region, and having the second conductivity type;and a sixth semiconductor region located in the additional semiconductormaterial adjacent to the fourth semiconductor region and having thefirst conductivity type, wherein no portion of the second semiconductorregion is located under the sixth semiconductor region.
 12. Thesemiconductor device of claim 11, further comprising epitaxially grownsemiconductor material located above the buried oxide layer, wherein:the first semiconductor region comprises a portion of the epitaxiallygrown semiconductor material; and the second semiconductor region, thethird semiconductor region, the fourth semiconductor region, and thefifth semiconductor region are all located in the epitaxially grownsemiconductor material.
 13. The semiconductor device of claim 11,further comprising a semiconductor contact region located in the fifthsemiconductor region and having the second conductivity type, whereinthe fifth semiconductor region electrically couples the secondsemiconductor region to the semiconductor contact region.
 14. Thesemiconductor device of claim 11, further comprising: a layer ofsemiconductor material overlying the buried oxide layer; and epitaxiallygrown semiconductor material overlying the layer of semiconductormaterial; wherein: the first semiconductor region comprises a portion ofthe epitaxially grown semiconductor material; and the secondsemiconductor region, the third semiconductor region, the fourthsemiconductor region, and the fifth semiconductor region are all locatedin the epitaxially grown semiconductor material.
 15. A semiconductordevice comprising: a semiconductor-on-insulator substrate comprising asupport layer, a buried insulator layer overlying the support layer, anda layer of semiconductor material overlying the buried insulator layer;additional semiconductor material overlying the layer of semiconductormaterial, the additional semiconductor material comprising a firstsemiconductor region having a first conductivity type; a secondsemiconductor region located in the additional semiconductor materialand having a second conductivity type; a third semiconductor regionlocated in the additional semiconductor material above the secondsemiconductor region and having the first conductivity type; a fourthsemiconductor region located in the additional semiconductor materialabove the third semiconductor region and having the second conductivitytype; a fifth semiconductor region located in the additionalsemiconductor material above the second semiconductor region and havingthe second conductivity type, the fifth semiconductor region beingadjacent to both the third semiconductor region and the fourthsemiconductor region, wherein the fifth semiconductor regionelectrically couples the second semiconductor region and the fourthsemiconductor region to a semiconductor contact region; and a sixthsemiconductor region located in the additional semiconductor materialadjacent to the fourth semiconductor region and having the firstconductivity type; wherein: no portion of the second semiconductorregion is located under the sixth semiconductor region; no portion ofthe third semiconductor region is located under the sixth semiconductorregion; and the fourth semiconductor region separates the fifthsemiconductor region from the sixth semiconductor region.